One of Facebook CEO Mark Zuckerberg’s top lieutenants unexpectedly quit Thursday following news that federal prosecutors are investigating the company’s use of private data.

Chris Cox was put in charge of some of Facebook’s most important features, including Instagram, Messenger, and WhatsApp,- which together have over 2.7 billion users worldwide. Cox, who has been with the company for 13 years, announced his departure in a blog post Thursday without explaining what led to his exit.

“It is with great sadness I share with you that after thirteen years, I’ve decided to leave the company,” Cox wrote in his post. “Since I was twenty-three, I’ve poured myself into these walls. This place will forever be a part of me.”

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Zuckerberg said in a separate blog post on the same day that the veteran executive had considered moving on several years ago but stayed around after 2016. News of Cox’s departure comes after a grand jury in New York subpoenaed records from two smartphone developers. Both companies entered into large and complex data deals with Facebook, allowing all the firms involved in the partnership to collect vast troves of information on millions of users.

The agreements allowed companies such as Amazon, Apple and Microsoft, among others, to see users’ friends and contact information, often without consent. The Department of Justice began probing the Silicon Valley company after a report showed Cambridge Analytica, a political consulting firm, used the platform to improperly obtained data on 87 million people to help President Donald Trump’s campaign.

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